This invention relates to a process for converting a carboxamide to a N-substituted derivative thereof, and particularly to a method for determining the conversion of said carboxamide to said derivative.
The Mannich reaction of carboxamides, particularly acrylamide or polymers thereof, with a lower aldehyde such as formaldehyde and a secondary amine such as dimethylamine to form a N-(aminoalkyl) derivative is well known. See U.S. Pat. Nos. 2,328,901; 3,256,140 and 3,539,535. As has been reported, this Mannich reaction involves the condensation of the carboximide, an aldehyde, usually formaldehyde, and a secondary amine. It is generally well accepted that the reaction normally involves the condensation of N-hydroxymethylamine or methylenediamine with the carboxamide containing a labile hydrogen under both acidic and basic conditions. While the mechanism and reaction kinetics for the Mannich reaction are reasonably well understood, it has not been a practice of the art to detect and control the conversion of the carboxamide to the desired Mannich derivative with any degree of accuracy. As a result, such reactions have generally been carried out in a somewhat haphazard and unpredictable fashion resulting in the formation of products which are inconsistent as to their conversion and purity. Such products are generally less efficient than theoretical calculations would indicate.
Accordingly, it would be highly desirable to provide a method for detecting and controlling the quantitative conversion of carboxamide to N-substituted derivative in order to produce optimum yields of an N-substituted derivative of more uniform product quality.